1. Field of the Invention
The present invention relates to a wireless LAN or other wireless communication system equipped with access points and wireless stations which communicate wirelessly with other stations via the access points, the access points and wireless stations composing the wireless communication system, and a communication load balancing method for the access points.
2. Description of the Related Art
As is well known, in wireless LAN, access points (hereinafter abbreviated to APs) and wireless stations are connected via wireless communications. Multiple APs are connected with each other via wired LAN and connected to a public network such as the Internet via routers or other nodes as required. Generally wireless stations are mobile, and thus it is necessary to switch from the current AP to an adjacent AP as they move. Thus, each wireless station measures the intensity of electromagnetic waves received from APs, and when the electromagnetic waves received from the currently connected AP decrease in intensity along with the movement of the wireless station, it switches to an adjacent AP, making it possible to continue wireless communications.
If a large number of wireless stations happen to concentrate around one AP, resulting in an increase in the number of wireless stations connected to the AP, the AP will be overloaded, causing reductions in wireless transfer speed. This may even disable the wireless communication. To prevent such a situation, there is a technique called load balancing. Known load balancing techniques include the one described in Patent Document 1.
This technique avoids concentration of loads on a single AP by including quantity information about the wireless stations connected to the AP in a beacon transmitted from the AP and making each wireless station determine whether to switch to an adjacent AP based on the quantity information and intensity of the electromagnetic waves received from the current AP. More specifically, the wireless station receives quantity information from each AP, determines whether there is an AP which is connected with less wireless stations by a predetermined number than is the currently connected AP, and switches to any such AP provided that the intensity of electromagnetic waves received from the AP is higher than a predetermined level.
[Patent Document 1]: Japanese Patent Publication No. 2002-359864
However, with the conventional technique, if a large number of wireless stations are located very close to a given AP, the electromagnetic waves received from any other AP is weaker than those received from the given AP and thus the wireless stations do not switch to another AP. Consequently over load status of the AP cannot be corrected.